Installation, integration and first operating experiences of the ALICE ITS upgraded readout system

The ALICE inner tracking system has gone through a significant upgrade for the upcoming third running period of the CERN LHC. The new detector consists of seven layers of high-granularity pixel sensors, while 192 custom FPGA-based readout units control the sensors and transmit the data upstream for analysis. This contribution describes the current system status and the expertise gained by moving from surface commissioning to the installation and throughout the data-taking preparation period, focusing on the intricate integration with other system components. Selected challenges, issues, and lessons learned during the various commissioning periods are presented.